Zyxel router problem - says it's resetting continuously

I recently bought a Zyxel 660H router as we are due to get ADSL
tomorrow or the next day. I bought it on the strength of a Zyxel 334
router that I had already bought in anticipation of Wireless
Broadband which has yet to arrive after never-ending delays.

Both these routers have a facility called "Traffic Redirect" which
reroutes requests from the router (as default gateway on the subnet)
to an alternative gateway on the same subnet. I had this set up on
the Zyxel 334 so that it redirected to my ISDN router and that worked
perfectly - the Zyxel 334 was the default route for all machines on
the network and in the absence of the Wireless Broadband all traffic
went via the ISDN router.

On getting the 660H router I configured it the same was as I had
configured the 334 router (not trivial as the menus are completely
different) and it didn't work - at least it didn't redirect to the
ISDN router at all. So I took a look at the Zyxel support site and
downloaded the latest drivers for the 660H, the release notes had an
entry which suggested that there was a fix for Traffic Redirect not
working so I installed the latest drivers.

Initially all seemed well, the traffic redirect appeared to start
working. However there is now another problem, after a while the
Router goes crazy. The power light starts flashing indicating that it
is rebooting - but it does it for ever until powered down and up
again. In addition the DSL connection light goes out, whereas it
should be flashing as the connection is there, just not activated.

Has anyone else had problems with Zyxel routers like this?

I can revert to the original firmware but then I lose the Traffic
Redirect ability which is one of the specific reasons that I bought
the router.

[Follow-ups directed to uk.comp.home-networking]

--
Chris Green